Periodic porous 3D boron-doped diamond electrode for enhanced perfluorooctanoic acid degradation

Abstract

Using diamond anodes for electrochemical removal of recalcitrant perfluorooctanoic acid (PFOA) pollutants has become an important strategy in recent research. However, the electrolysis removal efficiency of PFOA is still plagued by low electrochemical active surface area (EASA) and mass transfer limitation of conventional flat-plate diamond anodes. Herein, the periodic porous boron-doped diamond (PP-BDD) anodes were successfully prepared by 3D printing combined with hot-filament chemical vapor deposition (HF-CVD) technologies. The prepared PP-BDD anode achieves a higher PFOA kinetics (kapp = 0.022 min−1, the normalized rate constant is 6.6 m s−1) compared with the conventional 2D-BDD anode (kapp = 0.006 min−1, the normalized rate constant is 1.8 m s−1) at the applied density of 20 mA cm−2. The calculated mass transfer coefficient km of PFOA towards PP-BDD (2.6 × 10−5 m s−1) is about 6.1 times higher than that of 2D-BDD (0.42 × 10−5 m s−1), and the electron paramagnetic resonance (EPR) measurement verifies that PP-BDD produces more •OH and SO4•− radicals during the electrolysis process versus 2D-BDD. The unique periodic pore structure enables PP-BDD higher EASA than 2D-BDD and increases the mass transfer efficiency. Consequently, the number of electrolyte and PFOA molecule accessible diamond anode surface is increased. This work provides valuable guidance for the deterministic design of periodic pore structure-based BDD electrodes for efficient electrochemical oxidation (EO) of refractory pollutants.